O'Rourke's politics are closer to those of Sanders, the independent Vermont senator and 2016 presidential contender, than Cruz, and for that matter, Texas Gov. Greg Abbott or any other Texas Republican.

The ideological differences between Cruz and O'Rourke are as clear as an August Texas sky, minus the pollution.

O'Rourke's challenge is to attract Republican voters, even though he's not in step with how they would approach important issues.

Yet, in some instances he appears to be reaching Republican voters. There are yards in GOP areas that contain O'Rourke signs. They are planted with signs for down-ballot Republican candidates. O'Rourke rallies have attracted some disenchanted Republicans who are turned off by Cruz or President Donald Trump.

(Provided/Home of former Garland Council member Rick Williams)

"Right now, more than ever, I'm seeing Democrats, but I'm also seeing Republicans, I'm seeing independents, I'm seeing folks who had given up on voting coming together," O'Rourke told me Monday in Dallas. "They are coming off the sidelines knowing that everything they care about, everything this county cares for, is at stake."

Beto O'Rourke, Democratic nominee for U.S. Senate, speaks at a rally at the Richardson Civic Center in Richardson on Aug. 14, 2018.

(Rose Baca/Staff Photographer)

Last week I covered the appearances of Cruz and O'Rourke in North Texas. They had contrasting appeals to voters. Though Cruz asked Democrats not satisfied with their party to join his ranks, the November Senate race hinges on whether O'Rourke can peel from Cruz's base.

That could be tough.

Here's a sampling of how O'Rourke is different from most Republicans.

— He's against building a wall to keep immigrants from illegally crossing the southern border, and supports a path to citizenship for the millions of people in the country without authorization who would have been part of the Deferred Action for Childhood Arrivals program that was scrapped in March.

— He wants to expand Medicaid and would push Texas to take federal funding under the Affordable Care Act. Abbott and former Gov. Rick Perry rejected to deal.

— As part of criminal justice reform, he would legalize marijuana to help end the prison pipeline that adversely impacts minority residents.

— He proposes spending tax dollars on early childhood education, including a proposal that would allot $10,000 a year per student.

— He would vote to impeach President Donald Trump.

Cruz is on the opposite side of all of those policy positions.

O'Rourke and Republican voters do have the framework of some ideas in common. They don't want to separate immigrant families that illegally crossed the border. They want Texas to be a great place to work and raise a family.

Perhaps that's why the El Paso congressman has staged a campaign that's brought him closer to winning a statewide contest than any Democrat since 1994. He's raising more campaign cash than Cruz, and he routinely attracts thousands of people at his rallies, including the 2,500 that flooded the Richardson Convention Center last Tuesday for a town hall meeting.

But it's going to take more than being a celebrity politician to win in November. And O'Rourke's star power obscures the structural advantage Republicans have in Texas general elections.

For instance, the Texas Organizing Project, a progressive group committed to criminal justice reform, estimates that 850,000 more Republicans vote in statewide elections than Democrats. That means O'Rourke must attract tens of thousands of Republicans to beat Cruz. How does he do that while supporting policies that Republican voters generally reject?

The other option for O'Rourke is pushing more progressive voters to the polls, including Hispanic residents who hold the key to the Democratic Party revival.

O'Rourke brushes off the political science.

"Everywhere I go folks will say, listen, 'I'm a Republican but I saw the work you did to expand mental health care for veterans ... Democrats who say we don't need a wall,'" he said. "Folks are not focused on what divides us. They're focused on the big things that we want to do."

Sounds familiar?

In some ways the 2018 O'Rourke campaign, at least in message, reminds me of Barack Obama's approach in the 2008 presidential race. With the country on the verge of economic collapse, Obama campaigned on hope and change, with little emphasis or details about policy.

America's voters needed the tonic of an uplifting campaign with a charismatic candidate they trusted. And Obama bolstered his message with a superior organization propelled by a strong base of Democratic Party voters, including African-Americans.

Fans get a chance to get close to Sen. Barack Obama after a speech at a rally at Reunion Arena in Dallas on February 20, 2008.

(File Photo/Vernon Bryant)

O'Rourke has a similar, positive message that's tailored for the era of Trump. He says he wants to be able to tell his children that when the country needed someone to stand up to the president and his policies, he did something.

"We'll need people who would typically sit home in a midterm election to come out," he said. "We'll need Republicans who might otherwise allow party to define who they would vote for to put their country first."

Indeed the backlash against Trump and the hunger for a winner has Texas Democrats excited. But it's hard to determine if that excitement for O'Rourke will attract enough non-Democrats to beat Cruz.

For his part, Cruz is confident that if conservatives vote he'll win, so he's making sure that he tries to define O'Rourke before segments of his base are captivated by his rival's positive, often addictive approach.

"Every penny that we raise is going to be used to mobilize, to energize, to turn out conservatives," Cruz said. "If we turn conservatives out, we will win all of our races. If conservatives stay home, we'll be in trouble."

O'Rourke says he smells trouble for Cruz.

"What I feel everywhere I go is that something great in Texas is coming together," O'Rourke said.